<html>
<head></head>
<body>
<input type="checkbox" id="awesome" /> <label for="awesome">Awesome!</label>
<style>
input[type="checkbox"] + label::before { content: '\a0'; /* non-break space */ display: inline-block; vertical-align: .2em; width: .8em; height: .8em; margin-right: .2em; border-radius: .2em; background: silver; text-indent: .15em; line-height: .65; }
input[type="checkbox"]:checked + label::before { content: '\2713'; background: yellowgreen; }
input[type="checkbox"] { position: absolute; clip: rect(0,0,0,0); }
</style>
</body>
</html>